The present invention relates to respirator appliances for the artificial ventilation of the pulmonary tracts of a user in accordance with a cycle of inspiratory and expiratory stages, of the kind comprising a supply circuit delivering a breathable gas, a utilisation circuit comprising an inhalation branch and an exhalation branch provided with an exhalation valve, a breathable gas accumulator forming a reserve buffer, a distributor connected to said supply circuit and comprising an inhalation valve in communication with said inhalation branch, an accumulator valve and a non-return valve which are both in communication with said accumulator, a cyclic-action control device which operates said inhalation outflow and accumulator valves according to a predetermined programme, and which is arranged to direct the breathable gas coming from the supply circuit and from said accumulator towards the inhalation branch during the inflow or breathing in stages, and the breathable gas coming from said supply circuit towards said accumulator during the exhalation stages. Hereinafter, such as respirator will be referred to as "of the kind described".
Respirators of the kind described in which the breathable gas is stored during the exhalation stage and then restored to the utilising circuit during the inhalation stage, are intended primarily for treatment of respiratory deficiencies or failures and may be utilised in hospital and home environments, or else as an emergency service.
The cyclic action control device renders it possible to supply the user with a ventilation, that is to say a given volume of breathable gas per unit of time, the parameters of which, in particular the frequency of the breathing cycles, the inhalation and exhalation periods and the ratio between these inflow and outflow periods, are displayed and modifiable at will. The ventilating operation may consequently easily be verified and controlled by the operative entrusted with the operation of the respirator, who is commonly a doctor.
French Patent Specification No. 76.07.945 filed Mar. 19, 1976, under the title "Respirator" describes a respirator of the kind described which is arranged adapt itself automatically to the pulmonary compliance and resistance of the user.
Exhaustive research performed in the sphere of artificial ventilation brought to light a particular number of problems which arise in medical practice, and the shortcomings of particular existing appliances. These problems are encountered mainly in two cases:
(a) that in which the ventilation controlled by the operative becomes inadequate for the patient, and
(b) That in which this ventilation becomes excessive for the patient, for example due to an obstruction of his pulmonary tracts during treatment.